1. Field of the Invention
The present invention relates to an in-vehicle electronic control apparatus incorporating a microprocessor and particularly to improvement of an in-vehicle electronic control apparatus, such as an engine control apparatus, which has a monitoring control circuit serially connected to the microprocessor in order to enhance the safety of the control.
2. Description of the Related Art
It is publicly known that, in an in-vehicle electronic control apparatus equipped with a microprocessor, a so-called Q&A-method abnormality determination unit is utilized in which, in order to always monitor whether or not the microprocessor functions normally, a monitoring control circuit is provided, the monitoring control circuit transmits question information to the microprocessor that serves as a main control circuit unit, the microprocessor sends answer information for the question information to the monitoring control circuit, and then the monitoring control circuit compares the sent answer information with correct-solution information that has preliminarily been provided and ascertains whether or not a normal answer has been obtained.
For example, according to Japanese Patent Laid-Open Pub. No. 2003-131734 (refer to FIG. 1, ABSTRACT, and Paragraphs [0035] through [0038]), there has been disclosed an abnormality monitoring method in which a control function is implemented in a control unit; there is provided a monitoring module that monitors the control function, and the monitoring module conveys question information to the control unit; the control unit calculates response information and conveys the response information to the monitoring module; and the monitoring module recognizes an error in the control function, based on the response information.
In a conventional apparatus disclosed in Japanese Patent Laid-Open No. 2003-131734; the control units to be monitored are in-vehicle control apparatuses such as an engine control apparatus, a transmission control apparatus, a steering control apparatus, and a brake control apparatus.
Additionally, according to Japanese Patent Laid-Open Pub. No. 2005-031865 (refer to FIG. 1, and ABSTRACT), there has been disclosed a technology in which an electronic control apparatus incorporating a microprocessor periodically and alternatively implements part of a control program so as to perform an operation inspection while the engine is running. The operation inspection is implemented in such a way that a monitoring control circuit unit sequentially transmits, through an inquiry packet, a great number of question items to a microprocessor that controls a group of electric loads in response to the contents of a nonvolatile program memory and the operation statuses of a group of input sensors, and compares the content of the reply from the microprocessor with correct-solution information so as to perform an abnormality determination; and the microprocessor diagnoses the cycle of reception of the inquiry packets so as to counter-monitor the monitoring operation of the monitoring control circuit unit.
The outline of the question/answer-method abnormality determination unit in conventional technology disclosed in Japanese Patent Laid-Open No. 2005-31865 is as illustrated in FIG. 23. That is to say, in FIG. 23, an electronic control apparatus 1 is configured with a main control circuit unit 2 incorporating a microprocessor 2a and a monitoring control circuit unit 3 serially connected to the main control circuit unit 2.
The main control circuit unit 2 is configured in such a way as to respond to the operation statuses of a great number of input signals including input signals A, B, and C and to output a great number of output signals including an output signal Y so as to drive and control the electric loads; the main control circuit unit 2 is configured in such a way that the control specification thereof is decided by the contents of a program memory 2b that collaborates with the microprocessor 2a. 
For example, a monitoring subject program 2c is configured in such a way as to calculate the output signal Y[=K×(A−B)+C], based on the input signals A, B, and C and a control constant K that is preliminarily stored in the program memory 2b. Simulated-calculation data 2f is stored in the program memory 2b; a table n that typifies data tables [1, 2, - - - , n] in the simulated-calculation data 2f is configured with the control constant K and simulation constants An, Bn, and Cn corresponding to the input signals A, B, and C, respectively; however, the electronic control apparatus 1 is configured in such a way that the table to be utilized for the simulated calculation is randomly designated in an updating manner, in accordance with question information from the monitoring control circuit unit 3.
The electronic control apparatus 1 is configured in such a way that, for the monitoring subject program 2c, an input information switching unit 2d periodically designates the data table n instead of the input signal A, B, and C, and the calculation result Yn[=K×(An−Bn)+Cn] is periodically transmitted, as answer information, to the monitoring control circuit unit 3 by way of an output destination switching unit 2e. In the monitoring control circuit unit 3, the correct-solution information corresponding to the question information (the data table number for simulated calculation) is preliminarily stored in a correct-solution information storage memory; an abnormality determination unit 3a compares the answer information obtained from the main control circuit unit 2 with the correct-solution information so as to determine whether or not an abnormality is caused.
In addition, as the control program for performing the simulated calculation utilizing the data table, the monitoring subject program 2c may directly be utilized, or a copy program 2g, which is the monitoring subject program 2c written in a different address region of the program memory 2b, may be utilized.
In the monitoring method, for the driving sequence control of a vehicle, according to Japanese Patent Laid-Open Pub. No. 2003-131734; various subject control units have been disclosed; however, neither efficient information transferring method nor efficient abnormality monitoring method for collectively monitoring the subject control units by a single control apparatus has been described. Accordingly, there has been a drawback that the monitoring control circuit unit cannot perform collective management of abnormality monitoring for an in-vehicle electronic control apparatus that collaborates with external control apparatuses, discrimination between an abnormality in the main control circuit unit and an abnormality in the external control apparatus, and abnormality processing in accordance with the contents of a detected abnormality.
Additionally, the monitoring control circuit unit in the electronic control apparatus disclosed in Japanese Patent Laid-Open No. 2005-31865 does not perform monitoring of diverse external connection apparatuses; neither efficient information transferring method nor efficient abnormality monitoring method for collectively monitoring the diverse external connection apparatuses is described. Accordingly, there has been a drawback that the monitoring control circuit unit cannot perform collective management of abnormality monitoring for an in-vehicle electronic control apparatus that collaborates with external control apparatuses, discrimination between an abnormality in the main control circuit unit and an abnormality in the external control apparatuses, and abnormality processing in accordance with the contents of a detected abnormality.
In each of the conventional technologies, there is left a problem that differentiation, upon detection of an abnormality, of a processing method cannot be achieved through management of discrimination between abnormality monitoring for the main control unit and abnormality monitoring for collaborating supplementary apparatuses.